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I'm trying to align the if's in the following MWE, but also keep the (n times) alignment intact. Applying the mechanism from Multiple = alignment and from Aligning conditions in cases environment, I still could not get it to work.

\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{amsmath} \begin{document} \begin{equation*} ns = \begin{cases} \quad s + s + ... + s & \text{ (n times) if } n > 0 \\ \quad\quad\quad 0 & \text{ if } n = 0 \\ \quad (-s) + (-s) + ...+ (-s) & \text{ (n times) if } n < 0 \end{cases} \end{equation*} \end{document}

Incidentally is there a way to remove the hideous \quad's ? (Does one question per question apply here?:)

Cases

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5 Answers 5

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You can use \hphantom in the second line to move the text over, or alternatively \hfill, as Mico mentions in a comment.

What's the purpose of the \quads anyway?

\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{amsmath} \begin{document} \begin{equation*} ns = \begin{cases} s + s + \dots + s & \text{ ($n$ times) if } n > 0 \\ 0 & \text{\hphantom{ ($n$ times)} if } n = 0 \\ (-s) + (-s) + \dots + (-s) & \text{ ($n$ times) if } n < 0 \end{cases} \end{equation*} \end{document}

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If you want to change the alignment for the columns in cases, one possibility is to define a new environment with the help of mathtools, as described in Right aligned first column in a cases environment For example, to have the first column centered, and the second right aligned :

\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{mathtools} \makeatletter \newcases{crcases}{\quad}{% \hfil$\m@th\displaystyle{##}$\hfil}{\hfil$\m@th\displaystyle{##}$}{\lbrace}{.} \makeatother \begin{document} \begin{equation*} ns = \begin{crcases} s + s + \dots + s & \text{ ($n$ times) if } n > 0 \\ 0 & \text{ if } n = 0 \\ (-s) + (-s) + \dots + (-s) & \text{ ($n$ times) if } n < 0 \end{crcases} \end{equation*} \end{document}

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  • The \quad's were to align the 0 near the center of the equations above and below. Commented Apr 24, 2017 at 21:25
  • ... should be \dots Commented Apr 24, 2017 at 21:30
  • 1
    In your first example, consider writing \hfill \text{if $n = 0$} instead of \text{\hphantom{ ($n$ times)} if } n = 0. Commented Apr 24, 2017 at 21:30
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With aligned (from amsmath package):

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\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{amsmath} \begin{document} \[ ns = \left\{\begin{aligned}\quad & s + s + \dotsm + s & \text{ ($n$ times) if } n & > 0 \\ & 0 & \text{ if } n & = 0 \\ & (-s) + (-s) + \dotsm + (-s) & \text{ ($n$ times) if } n & < 0 \end{aligned}\right. \] \end{document}
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  • +1 but I would say that \quad is excessively large. Also the n inside \text need to be in math mode. Commented Apr 25, 2017 at 7:15
  • @AndrewSwann, quad is left from OP MWE, I will reduce this distance. Similarly about n, I will correct this too. Commented Apr 25, 2017 at 7:41
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There should be a wider separation from “(n times)” to “if” than from the formulas and “(n times)”, in my opinion.

The 0 should be left flush, like the other two terms. I also fixed the math error (it should be |n| in the third line).

\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{amsmath} \begin{document} \begin{equation*} ns = \begin{cases} \begin{alignedat}{3} &s + s + \dots + s &\quad \text{($n$ times)} &\qquad& \text{if $n > 0$} \\ &0 &\quad &\qquad& \text{if $n = 0$} \\ &(-s) + (-s) + \dots + (-s) &\quad \text{($|n|$ times)} &\qquad& \text{if $n < 0$} \end{alignedat} \end{cases} \end{equation*} \end{document}

enter image description here

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4

And with simple array:

\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{amsmath} \begin{document} \begin{equation*} ns = \left \{ \begin{array}{lrl} s + s + \dots + s & (n \text{ times}) & \text{ if } n > 0 \\ 0 & & \text{ if } n = 0 \\ (-s) + (-s) + \dots + (-s) & (|n| \text{ times}) & \text{ if } n < 0 \end{array} \right. \end{equation*} \end{document}

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  • \right. Very clever! It makes this mechanism very powerful. Commented Apr 25, 2017 at 0:06
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With empheq, eqparbox and alignat*, which allows for several alignment points, and full control on the spacing between columns. I also propose another layout (better in my opinion) which requires onlycases`:

\documentclass[12pt,a4paper]{article} \usepackage[fleqn]{empheq} \usepackage{eqparbox} \newcommand\eqmathbox[2][M]{\eqmakebox[#1]{$ \displaystyle#2 $}} \usepackage[showframe]{geometry} \begin{document} \begin{empheq}[left = {ns=\empheqlbrace\,}]{alignat*=2} &\eqmathbox{s + s + \dots + s} & \text{ (n times) } & \text{if } n > 0 \\ & \eqmathbox{0} & & \text{if } n = 0 \\ & (-s) + (-s) + \dots+ (-s) & \qquad\text{ (n times) } & \text{if } n < 0 \end{empheq} \begin{equation*} ns = \begin{cases} \eqmathbox[C]{\,s + s + \dots + s} \text{\quad (n times)} & \text{ if } n > 0 \\ \eqmathbox[C]{\,0} & \text{ if } n = 0 \\ \, (-s) + (-s) + \dots + (-s) \text{\quad (n times)} & \text{ if } n < 0 \end{cases} \end{equation*} \end{document}

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